November 2018:  The solution consists of a single PervasID UHF RFID Space Ranger reader installed in the ceiling—provided that a store measures about 150 to 200 square meters (1,615 to 2,150 square feet) in size—along with antennas deployed in the receiving, storage and sales-floor areas, as well as in doorways.

https://www.rfidjournal.com/articles/view?17999/